1. Field of the Invention
The field of the invention relates to bifurcated or rectilinear tubular prostheses designed to be implanted in a human duct, or an animal duct, for maintaining or recovering a path therein.
2. Description of the Related Art
Especially, the invention applies to such a prosthesis to be disposed at the location of a vascular aneurism (in particular of the aorta) for isolating said aneurism, while creating there a substitute of the wall of the vessel, so that the blood can still circulate.
Various prostheses (or implants) designed to be disposed at the location of an aneurism are known, those prostheses being either self-expandable (viz. expandable without inner radial strength, through self elasticity or shape memory) or expandable by means of a complementary means creating an enlarging radial internal force (such as a balloon). Those prostheses generally comprise a metallic structure comprising at least one stent (or enlarger) adapted to be supported on the vessel wall, at least on one side of the aneurism, at a location called upper neck, by creating a force for enlarging the prosthesis towards the vessel wall.
The upper neck (or upstream neck) means the portion of the vessel wall located above the aneurism and lower neck means the portion of the vessel wall located just downstream the aneurism (relative to the blood flow).
Those prostheses are typically covered with a covering sheath which is disposed inside or outside the metallic structure and is (or becomes) impervious. They can be implanted in the vessel to be treated, for example through a transcutaneous, endoluminal way (in particular by the method called of SELDINGER) before self-expanding or before being expanded in said vessel and then fixed to the wall. This type of prostheses is in particular described in FR-A-2 732 404, U.S. Pat. Nos. 5,591,229, 5,330,500 or EP-A-0 696 447.
A problem is that those prostheses are generally insufficiently adapted to the implanting conditions, in particular at the upper neck of an aneurism. The shape of this neck (taken along its section, or longitudinally) is often not regular (curved, with a variable section, covered with various cellular aggregates or hollows) and very often different from one patient to another. Therefore, there is a hard adequation between the stent of the prosthesis and the wall of the duct. Furthermore, after a while, the duct tends to locally inflate under the action of the prosthesis and thus tends to be separated therefrom. Further, the prosthesis is sometimes incorrectly fixed to the duct and then risks to inopportunately move.
U.S. Pat. Nos. 5,527,355 or 5,507,378 describes a medical set designed to be implanted in an anatomical duct and comprising:
an intraluminal prosthesis comprising a structure adapted to take up a first radially constricted state, to be inserted into the duct, and a second radially unfolded state wherein the structure has a general shape of a single or bifurcated tube to rest, at least at its upper proximal end, against the wall of said duct, near the upstream zone thereof, and
at least a collar adapted to be disposed around the duct, in front of the proximal end of the prosthesis, for maintaining it against the duct when the set is implanted.
Nevertheless, an object of the invention is to provide a strap, or collar, for locally lining the zone of the duct wall to be treated with a view to improving the conditions of a laparoscopic implantation (also called coelioscopy or endoscopy), thus reducing the risks of the intervention (perforating the duct, alterating the nearby organs, . . . ) and making the intervention proceedings easier (easiness for moving the strap and the fixation of the strap and the prosthesis). Tightly maintaining the prosthesis is further requested.
The solution consists in using a collar which is, for its portion to be disposed in front of the anatomical duct to be treated, structured enough to be more rigid than a strap only, such as in U.S. Pat. No. 5,527,355.
In particular, the ring or collar used as sealing tight means outside and around the duct can comprise a core having the shape of a split ring naturally curved and resilient, the core being fixed to a flexible, elongated strap which is divisible and extends beyond the perimeter of the core. Thus, implementing a structured portion as a split ring is recommended.
Then, the advantage consists in having both a splitted ring adapted to be elastically disposed around the duct and a lace or strap, in particular made of fabric, which is very convenient for fitting the diameter of the sealing tight ring to the duct one.
According to another preferred feature of the invention, the core will be covered by a protecting covering made of a self-sealing material, while the covering covers the core at least over an external surface thereof (to be fixed thereto).
A specific application relates to using this prosthesis with its collar(s) at the location of the vascular aneurism, while the collar and the prosthesis are preferably disposed at the location of the upstream and downstream aneurism necks.
Using a radially deformable collar, which is preferably resiliently deformable, gives the opportunity to use an easily implantable means adapted to naturally fit the exact shape of the duct and the prosthesis. Further, designing a naturally adaptable means, viz. adapted to be disposed around ducts having various sections and pertaining to a sole patient or various patents, is allowed.
According to a further consideration, the prosthesis may comprise, in front of the (each) collar, a (further) radially deformable strengthener disposed within the corresponding duct, and consisting of at least an element or a portion of a metallic, annular structure so located that the duct wall is interposed between said element and the collar. Thus, if the duct is an aneurism, the prosthesis will still be further pressed to the duct wall. Furthermore, maintaining the prosthesis will be improved.
Together with, or in place of, this inner ring the prosthesis can be locally lined with an annular pad to be pressed to the internal, peripheral duct wall, for improving the sealing where the duct is squeezed.
According to a further consideration, the external surface of the above-mentioned inner ring can be slightly abrasive and/or non-skid for still accurately maintaining the implant in its receiving duct.
According to another feature, the invention takes into consideration the accuracy of implantation to be obtained, together with the easiness for the practitioner to fix the collar to the prosthesis, through the duct.
Therefore, it is recommended to include a radio-opaque mark within the collar, and in particular, to provide the core (or the strengthening structure) of this ring with two radio-opaque locating strips (for example made of metal) disposed substantially parallel and separated one from the other. Those strips delimit therebetween a zone defining, for the practitioner, a preferred zone for fixing the prosthesis.
For still improving the quality of the imperviousness, substantially whatever the duct perimeters are, said perimeters being allowed to change from one patient to another, a further feature of the invention recommends that the self-sealing protecting cover extends beyond the perimeter of the core, along the extended strands of the strap.
Thus, the practitioner will typically be in position to sealingly fix his collar to the prosthesis, through the duct. If necessary, he will adjust the length of this protecting cover by cutting it, since it is made of a divisible material (silicone, for example).
Further to the above-disclosed set, the invention relates to a method for implanting a prosthesis in its reception duct, the prosthesis being unfolded in situ, so that an external surface thereof is tightly pressed to an internal duct wall, at the location of an interface zone.
Preferably:
the external covering collar will be introduced around the corresponding zone(s) of the duct, through a percutaneous way (coelioscopy, in particular),
and the prosthesis will be percutaneously and endoluminally implanted, through said duct, and will be unfolded in the duct for obtaining a sealing barrier (seal) between the external surface of the prosthesis and the inner wall of the anatomical duct.
Advantageously:
the external lining collar will be introduced in its second state(substantially flat or with a very small diameter) in an introducing catheter, as far as the immediate vicinity of the external wall of the corresponding duct,
then, the collar will be pushed out of its introducing catheter for adopting its first state (curved) around the duct,
and it will be fixed to the prosthesis (already opened in the duct) by means of the above-mentioned fixation means brought near the prosthesis through coelioscopy (or laparoscopy) and thus introduced towards the prosthesis, from outside the duct, through the wall thereof.
It is to be noted that the invention further offers means to be used for improving the implantation of the external ring around the duct.
For this aim, the medical set will comprise:
a sheath, or a trocar, for a laparoscopy, adapted for introducing the collar within the patient body, up to the vicinity of the external wall of the duct,
and pliers for maneuvering the collar, the pliers being adapted to be slid in the sheath (or the trocar) beside the collar, the splitted annular portion of which is then opened to a stressed, substantially flat deformed position.
It will also be noted that, according to one aspect of the invention, the collar can be used as a lace for moving the corresponding duct, especially if the duct is a vessel.
In such a case, the surgeon will have to staunch one or more bleeding(s) from the vessel.
Thus, another feature of the invention recommends to provide the above-mentioned collar with an hemostatic structure, layer or cover, for reducing such a bleeding where the collar is pressed to the corresponding vessel.